Finding the domain of a function

y=(square root of x-3)
y=(square root of 2x+5)-7
f(x)=(square root of 9+x)

please help? Thanks.

ok so the square root of something can't be negative. So the thing under the radical has to be positive or zero. For the first one, x is all real numbers greater than or equal to 3. For the second one, x is all real numbers greater than or equal to -2.5. For the third one, x is all real number greater than or equal to -9.

y=(square root of x-3) = (x-3)^1/2 >>>>> domain is [ 3 , infinity)
y=(square root of 2x+5)-7 = (2x+5)^1/2 -7 >>>> 2x+5 >= 0 , x >= -5/2 ////domain= [ -5/2 , infinity )
f(x)=(square root of 9+x) = (9+x)^1/2 >>>> 9+x >= 0 , x >= -9 /////domain = [ -9 , infinity)